map -package:containers -package:charset -package:dense-linear-algebra -package:blaze-html -package:case-insensitive is:exact -package:invertible -package:base-prelude -package:base-compat-batteries -package:monoidal-containers -package:bytestring package:pipes

Apply a function to all values flowing downstream
map id = cat

map (g . f) = map f >-> map g